Seven speed dual clutch transmission

ABSTRACT

A transmission connectable to an input member and having an output transfer gear, first and second transmission input shaft members, first and second countershaft members, an idler shaft, a plurality of co-planar gear sets, and a plurality of torque transmitting devices. The torque transmitting devices include a plurality of synchronizer assemblies and a dual clutch assembly. The transmission is operable to provide at least one reverse speed ratio and a plurality of forward speed ratios between the transmission input members and the output member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/764,612, filed on Apr. 21, 2010, which claims priority to U.S.Provisional Application No. 61/177,426, filed on May 12, 2009, which areboth hereby incorporated in its entirety herein by reference.

TECHNICAL FIELD

The present disclosure relates to transmissions and more particularly toa compact, dual clutch multiple speed transmission having three axes toestablish seven or more gear speeds.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may or may not constitute priorart.

A typical multiple speed transmission having countershafts and co-planargear sets uses countershaft gears with a different, dedicated gear pairor set to achieve each forward speed ratio. Accordingly, the totalnumber of gears required in this typical design is two times the numberof forward speeds, plus three for reverse. This necessitates a largenumber of required gear pairs, especially in transmissions that have arelatively large number of forward speed ratios.

While current transmissions achieve their intended purpose, the need fornew and improved transmission configurations which exhibit improvedperformance, especially from the standpoints of efficiency,responsiveness and smoothness and improved packaging, primarily reducedsize and weight, is essentially constant. Accordingly, there is a needin the art for a transmission having improved packaging while providingdesirable gear ratios and torque ranges.

SUMMARY

The present invention provides a transmission having first and secondtransmission input members, an output member, first and secondcountershaft members, a plurality of co-planar gear sets, and aplurality of torque transmitting devices. The torque transmittingdevices include a plurality of synchronizer assemblies and a dual clutchassembly. The transmission is operable to provide at least one reversespeed ratio and a plurality of forward speed ratios between thetransmission input members and the output member.

In one aspect of the present invention, the transmission has atransmission housing and a dual clutch assembly having a clutch housingconnectable to a flywheel or other engine output member. The clutchhousing is rotationally supported within the transmission housing.

In yet another aspect of the present invention, the transmissionprovides a first, a second, a third, a fourth and a fifth gear set. Thefirst gear set has a first gear in mesh with a second gear, the secondgear set has a first gear in mesh with a second gear and a third gear,the third gear set has a first gear in mesh with a second gear and athird gear, the fourth gear set has a first gear in mesh with a secondgear and the fifth gear set has a first gear in mesh with a second gear.

In yet another aspect of the present invention, the second gear of thefirst gear set is a stepped pinion gear having a first and a second gearteeth portions, and wherein the first gear teeth portion is larger thanthe second gear teeth portion and meshes with the first gear of thefirst gear set and the second gear teeth portion meshes with a reversegear.

In yet another aspect of the present invention, a first transmissioninput member has a first end portion and a second end portion rotatablysupported in the transmission housing. Each of the first gear of thethird, fourth and fifth gear sets are rotatably fixed for commonrotation with the first transmission input member.

In yet another aspect of the present invention, a second transmissioninput member has a first end portion and a second end portion rotatablysupported in the transmission housing. Each of the first gear of thefirst and second gear sets are rotatably fixed for common rotation withthe second transmission input member. The second transmission inputmember is concentric with the first transmission input member and atleast partially surrounds the first transmission input member.

In still another aspect of the present invention, a first countershaftis rotatably supported within the transmission housing and spaced apartfrom and parallel with the first and second transmission input members.The reverse gear, the third gear of the second gear set, the third gearof the third gear set and the second gear of the fourth gear set areeach selectively connectable for common rotation with the firstcountershaft.

In still another aspect of the present invention, a second countershaftis rotatably supported within the transmission housing and spaced apartfrom and parallel with the first and second transmission input members.The second gear of the first gear set, the second gear of the secondgear set, the second gear of the third gear set and the second gear ofthe fifth gear set are each selectively connectable for common rotationwith the second countershaft.

In still another aspect of the present invention, a first synchronizerassembly selectively connects at least one of the second gear of thefirst gear set and the second gear of the second gear set to the secondcountershaft.

In still another aspect of the present invention, a second synchronizerassembly selectively connects at least one of the reverse gear and thirdgear of the second gear set to the first countershaft.

In still another aspect of the present invention, a third synchronizerassembly selectively connects at least one of the second gear of thethird gear set and the second gear of the fifth gear set to the secondcountershaft.

In still another aspect of the present invention, a fourth synchronizerassembly selectively connects at least one of the third gear of thethird gear set and the second gear of the fourth gear set to the firstcountershaft.

In still another aspect of the present invention, a first countershafttransfer gear is fixed to the first countershaft for common rotationwith the first countershaft and a second countershaft transfer gearfixed to the second countershaft for common rotation with the secondcountershaft. The first and second countershaft transfer gears transfertorque from at least one of the first and second countershafts to anoutput member.

In still another aspect of the present invention, a park gear is fixedto a first end of a park gear shaft and a park transfer gear is fixed toa second end of the park gear shaft. The park transfer gear meshes withthe transmission output member and the park gear is configured toprevent rotation of the transmission output member when the park gear isengaged.

In still another aspect of the present invention, a park gear is fixedto the first countershaft. The park gear is configured to preventrotation of the first countershaft and the transmission output memberwhen the park gear is engaged.

In still another aspect of the present invention, the selectiveengagement of dual clutch assembly interconnects the dual clutch housingwith at least one of the first and the second transmission input membersand the selective engagement of at least one of the synchronizerassemblies establishes at least one of seven forward speed ratiosbetween the at least one of the first and the second transmission inputmembers and the output member.

The above features and advantages and other features and advantages ofthe present invention are readily apparent from the following detaileddescription of the best modes for carrying out the invention when takenin connection with the accompanying drawings wherein like referencenumbers refer to the same component, element or feature.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic view of an embodiment of a seven speedtransmission having a park gear mounted on a separate park shaft, inaccordance with the present invention; and

FIG. 2 is a schematic view of an embodiment of a seven speedtransmission having a park gear mounted on a countershaft, in accordancewith the present invention.

DESCRIPTION

Referring to FIG. 1, a multiple speed transmission is generallyindicated by reference number 10. The transmission 10 is connectable toan input member 12 and has an output member or gear 14. In the presentembodiment, the input member 12 is a shaft and the output member 14 is agear, however those skilled in the art will appreciate that the inputmember 12 may be components other than shafts and the output member 14may be a component, such as a shaft, other than a gear.

The input member 12 is continuously connected with an engine (not shown)or other torque producing machine to provide a driving torque to inputmember 12. The output member or gear 14 rotatably drives a differentialassembly 16. The differential assembly 16 transfers torque delivered byoutput member 14, ultimately, to a pair road wheels (not shown).

The transmission 10 includes a housing 18 that at least partiallyencloses a gearing arrangement 20. The gearing arrangement 20 includesvarious shafts or members, co-planar intermeshing gear sets, a dualclutch assembly, and selectively engageable synchronizers, as will bedescribed herein. For example, the gearing arrangement 20 includes afirst transmission input shaft or member 22, a second transmission inputshaft or member 24, a first countershaft 26, a second countershaft 28and park gear shaft 30. The second transmission input shaft or member 24is a sleeve (hollow) shaft that is concentric with and overlies thefirst transmission input shaft or member 22. The first countershaft 26,the second countershaft 28 and the park gear shaft 30 are each spacedapart from and parallel with the first and second transmission inputshaft members 22, 24. The first and second transmission input shafts 22,24 define a first axis of rotation, the first countershaft 26 defines asecond axis of rotation and the second countershaft 28 defines a thirdaxis of rotation. The position and location of countershafts 26 and 28relative to first and second transmission input shafts 22, 24 areinterchangeable.

A dual clutch assembly 32 is connected between the input member 12 andthe first and second transmission input shaft members 22, 24. The dualclutch assembly 32 includes a clutch housing 34 connectable for commonrotation with the input member 12. Further, the dual clutch assembly 32has first and second clutch elements or hubs 36 and 38. Clutch elements36 and 38 together with the clutch housing 34 are configured to form afriction clutch, as is known in the art as a dual clutch. Morespecifically, clutch elements 36, 38 and the clutch housing 34 havefriction plates mounted thereon or otherwise coupled thereto thatinteract to form a friction clutch. The clutch element 36 is connectedfor common rotation with the first transmission input shaft or member 22and the clutch element 38 is connected for common rotation with thesecond transmission input shaft or member 24. Thus, selective engagementof clutch element 36 with the clutch housing 34 connects the inputmember 12 for common rotation with the first transmission input shaftmember 22. Selective engagement of clutch element 38 with the clutchhousing 34 connects the input member 12 for common rotation with thesecond transmission input shaft member 24.

The gearing arrangement 20 also includes a plurality of co-planar,meshing gear sets 40, 50, 60, 70 and 80. The present inventioncontemplates that the plurality of co-planar, meshing gear sets 40, 50,60, 70 and 80 may be arranged axially along transmission input shafts22, 24 in an order other than that which is shown in FIG. 1 and still bewithin the scope of the invention. Co-planar gear set 40 includes gear42 and gear 44. Gear 42 is rotatably fixed and connected for commonrotation with the second transmission input shaft member 24. Gear 44 isselectively connectable for common rotation with the second countershaftmember 28 and meshes with gear 42. Gear 44 includes a secondary gearportion 46 that is kinematically connected to and fixed for commonrotation with gear 44. Secondary gear portion 46 may have the same or adifferent gear tooth count or gear pitch relative to other portions ofgear 44, as necessary to implement a desired reverse gear ratio. Itshould be appreciated that gear 42 may be a separate gear structurefixed to the second transmission input shaft member 24 or gearteeth/splines formed on an outer surface of the second transmissioninput shaft member 24 without departing from the scope of the presentinvention. Gear set 40 is disposed proximate a wall 48 of thetransmission housing 18 that is on a front or side of the transmission10 proximate the dual clutch assembly 32.

Co-planar gear set 50 includes gear 52, gear 54 and gear 56. Gear 52 isrotatably fixed and connected for common rotation with the secondtransmission input shaft member 24 and meshes with gear 54 and gear 56.Gear 54 is selectively connectable for common rotation with the secondcountershaft member 28. Gear 56 is selectively connectable for commonrotation with the first countershaft member 26. Gear set 50 ispositioned adjacent gear set 40.

Co-planar gear set 60 includes gear 62, gear 64 and gear 66. Gear 62 isrotatably fixed and connected for common rotation with the firsttransmission input shaft member 22 and meshes with gear 64 and gear 66.Gear 64 is selectively connectable for common rotation with the secondcountershaft member 28. Gear 66 is selectively connectable for commonrotation with the first countershaft member 26. Gear set 60 is disposedadjacent gear set 50.

Co-planar gear set 70 includes gear 72 and gear 74. Gear 72 is rotatablyfixed and connected for common rotation with the first transmissioninput shaft member 22 and meshes with gear 74. Gear 74 is selectivelyconnectable for common rotation with the first countershaft member 26.Gear set 70 is positioned adjacent gear set 60.

Co-planar gear set 80 includes gear 82 and gear 84. Gear 82 is rotatablyfixed and connected for common rotation with the first transmissioninput shaft member 22 and meshes with gear 84. Gear 84 is selectivelyconnectable for common rotation with the second countershaft member 28.Gear set 80 is positioned between gear set 70 and an end wall 88 of thetransmission housing 18.

Reverse gear 90 is selectively connectable for common rotation with thefirst countershaft member 26 and meshes with a secondary gear portion 46of stepped gear 44. As described previously, secondary gear portion 46of gear 44 is fixed for common rotation with gear 44 and may have adifferent gear pitch than the gear pitch of gear 44, as required, toimplement a reverse gear speed. Reverse gear 90 is located between gearset 50 and end wall 48. Reverse gear 90 and secondary gear portion 46may be considered to be a sixth co-planar gear set.

Further, a first countershaft transfer gear 100 is rotatably fixed andconnected for common rotation with the first countershaft member 26. Asecond countershaft transfer gear 110 is rotatably fixed and connectedfor common rotation with the second countershaft member 28. A parktransfer gear 111 is rotatably fixed and connected for common rotationwith the park gear shaft 30. First countershaft transfer gear 100 isconfigured to mesh with output member 14, the second countershafttransfer gear 110 is configured to mesh with output member 14 and parktransfer gear 111 is configured to mesh with output member 14. However,the first countershaft transfer gear 100 the second countershafttransfer gear 110 and the park transfer gear 111 do not mesh with eachother. The first countershaft transfer gear 100 is disposed between thereverse gear 90 and end wall 48 of the transmission housing 18. Thesecond countershaft transfer gear 110 is disposed between gear 44 andend wall 48 of the transmission housing 18. The park transfer gear 111is disposed proximate to wall 48 of transmission housing 18 andco-planar with output gear or member 14. Moreover, the output member 14is co-planar with first and second countershaft transfer gears 100, 110.

A park gear 112 is provided for placing transmission 10 in a park modethat prevents output member 14 from rotating. Park gear 112 is coupledto park transfer gear 111 through park gear shaft 30. Alternatively, asshown in FIG. 2 as transmission 10′, the present invention contemplatesfixedly disposing park gear on one of the first and second countershaftsto achieve the park mode function. In the transmission 10′ embodiment,the park transfer gear 111 and park gear shaft 30 are eliminated furtherimproving packaging capability of the transmission. Moreover, the axiallocation of park gear 112 along the countershafts 26 or 28 may bechanged in accordance with available packaging space.

With continued reference to FIG. 1, the transmission 10 further includesa plurality of selectively engageable synchronizer assemblies 150, 152,154 and 156. Synchronizers 150, 152, 154 and 156 are double sidedsynchronizers and generally include a shift fork (not shown) that isbi-directionally translated by an actuator (not shown) into at least twoengaged positions and a neutral or disengaged position. In the presentembodiment, synchronizer 150 is selectively actuatable to connect gear44 for common rotation with the second countershaft member 28 andsynchronizer 150 is selectively actuatable to connect gear 54 for commonrotation with the second countershaft member 28. Synchronizer 152 isselectively actuatable to connect for common rotation reverse gear 90with the first countershaft 26 and is selectively actuatable to connectfor common rotation gear 56 with the first countershaft 26. Synchronizer154 is selectively actuatable to connect for common rotation gear 64with the second countershaft 28 and is selectively actuatable to connectfor common rotation gear 84 with the second countershaft 28.Synchronizer 156 is selectively actuatable to connect for commonrotation gear 66 with the first countershaft member 26 and isselectively actuatable to connect for common rotation gear 74 with thefirst countershaft member 26.

The transmission 10 is capable of transmitting torque from the inputshaft 12 to the output gear member 14 in at least seven forward torqueratios and at least one reverse torque ratio. Each of the forward torqueratios and the reverse torque ratio is attained by selective engagementof the dual clutch assembly 32 and one or more of the synchronizerassemblies 150, 152, 154 and 156. Those skilled in the art will readilyunderstand that a different speed ratio is associated with each torqueratio.

It should be appreciated that each individual gear set 40, 50, 60, 70and 80 provides one or more forward and/or reverse gear ratios uponselective engagement of the synchronizer assemblies 150, 152, 154 and156. It should also be appreciated that a particular forward or reversespeed ratio may be achieved by different combinations of synchronizerand associated gear sets without departing from the scope of the presentinvention.

For example, to establish the reverse torque ratio, clutch element 38 isengaged and synchronizer 152 is activated. Clutch element 38 couples theinput member 12 with the second transmission input shaft member 24.Synchronizer 152 connects reverse gear 90 to the first countershaftmember 26. More specifically, input torque from the input shaft 12 istransferred through the dual clutch assembly 32 to the secondtransmission input shaft member 24, through gear 42 to gear 44, throughthe secondary gear portion 46 of gear 44 to reverse gear 90, from gear90 to the first countershaft member 26 through synchronizer 152 to firstcountershaft transfer gear 100 and from first countershaft transfer gear100 to the output member 14.

To establish a first forward torque ratio (i.e. a 1st gear), clutchelement 36 is engaged and synchronizer 156 is activated. Clutch element36 couples the input member 12 with the first transmission input shaftmember 22. Synchronizer 156 couples gear 74 to the first countershaftmember 26. Input torque from the input member 12 is transferred throughthe dual clutch assembly 32 to the first transmission input shaft member22 to gear 72. Gear 72 transfers torque to gear 74 which transfers thetorque to the first countershaft member 26 through synchronizer 156 andto first countershaft transfer gear 100 and then from first countershafttransfer gear 100 to the output member 14.

To establish a second forward torque ratio (i.e. a 2nd gear), clutchelement 38 is engaged and synchronizer 150 is activated. Clutch element38 couples the input member 12 to the second transmission input shaftmember 24 which rotates gear 42. Synchronizer 150 couples gear 44 to thesecond countershaft member 28. Accordingly, input torque from the inputmember 12 is transferred through the dual clutch assembly 32 to thesecond transmission input shaft member 24, through gear 42 to gear 44,from gear 44 to synchronizer 150, from synchronizer 150 to the secondcountershaft member 28 and from the second countershaft member 28 to thesecond countershaft transfer gear 110 and the output member 14.

To establish a third forward torque ratio (i.e. a 3rd gear), clutchelement 36 is engaged and synchronizer 154 is activated. Clutch element36 couples the input member 12 to the first transmission input shaftmember 22 which rotates gear 82. Synchronizer 154 couples gear 74 to thesecond countershaft member 28. Thus, input torque from the input member12 is transferred through the dual clutch assembly 32 to the firsttransmission input shaft member 22, through gear 82 to gear 84, throughgear 84 to synchronizer 154, from synchronizer 154 to the secondcountershaft member 28, from the second countershaft member 28 to thesecond countershaft transfer gear 110 and then from second countershafttransfer gear 110 to the output member 14.

To establish a fourth forward torque ratio (i.e. a 4th gear), clutchelement 38 is engaged and synchronizer 152 is activated. Clutch element38 couples the input member 12 to the second transmission input shaftmember 24 which rotates gear 52. Synchronizer 152 couples gear 56 to thefirst countershaft member 26. Thus, input torque from the input member12 is transferred through the dual clutch assembly 32 to the secondtransmission input shaft member 24 to gear 52, then from gear 52 to gear56, from gear 56 to synchronizer 152, from synchronizer 152 to the firstcountershaft member 26, from the first countershaft member 26 to firstcountershaft transfer gear 100 and then from first countershaft transfergear 100 to the output member 14.

To establish a fifth forward torque ratio (i.e. a 5th gear), clutchelement 36 is engaged and synchronizer 156 is activated. Clutch element36 couples the input member 12 to the first transmission input shaftmember 22 which rotates gear 62. Synchronizer 156 couples gear 66 to thefirst countershaft member 26. Input torque from the input member 12 istransferred through the dual clutch assembly 32 to the firsttransmission input shaft member 22, from first transmission input shaftmember 22 to gear 62, from gear 62 to gear 66, from gear 66 to the firstcountershaft member 26 through synchronizer 156, to first countershafttransfer gear 100 and from first countershaft transfer gear 100 to theoutput member 14.

To establish a sixth forward torque ratio (i.e. a 6th gear), clutchelement 38 is engaged and synchronizer 150 is activated. Clutch element38 couples the input member 12 to the second transmission input shaftmember 24 which rotates gear 52. Synchronizer 150 couples gear 54 to thesecond countershaft member 28. Thus, input torque from the input member12 is transferred through the dual clutch assembly 32 to the secondtransmission input shaft member 24 to gear 52, then from gear 52 to gear54, from gear 54 to synchronizer 150, from synchronizer 150 to thesecond countershaft member 28, from the second countershaft member 28 tosecond countershaft transfer gear 110 and then from second countershafttransfer gear 110 to the output member 14.

To establish a seventh forward torque ratio (i.e. a 7th gear), clutchelement 36 is engaged and synchronizer 154 is activated. Clutch element36 couples the input member 12 to the first transmission input shaftmember 22 which rotates gear 62. Synchronizer 154 couples gear 64 to thesecond countershaft member 28. Input torque from the input member 12 istransferred through the dual clutch assembly 32 to the firsttransmission input shaft member 22, from first transmission input shaftmember 22 to gear 62, from gear 62 to gear 64, from gear 64 to thesecond countershaft member 28 through synchronizer 154, to secondcountershaft transfer gear 110 and from second countershaft transfergear 110 to the output member 14.

Again, it should be appreciated that any one of the gear sets of gearsets 40, 50, 60, 70 and 80 may be changed to produce a certain forwardand reverse torque ratio without departing from the scope of the presentinvention.

The present invention contemplates that a variety of torque ratios(i.e., the ratio of torque of the output member 14 to the input member12) and ratio steps are achievable through the selection of tooth countsof the gears of the transmission 10. The present invention has manyadvantages and benefits over the prior art. For example, the utilizationof four synchronizers allows the use of four rails having one fork oneach rail. Thus, a transmission having a more simplified actuation andcontrol system, reduced mass and cost and improved packaging isachieved.

While the best modes for carrying out the invention have been describedin detail, those familiar with the art to which this invention relateswill recognize various alternative designs and embodiments forpracticing the invention within the scope of the appended claims.

The invention claimed is:
 1. A powertrain comprising: an engine outputmember; a transmission housing; a dual clutch assembly having a clutchhousing connected to the engine output member, wherein the clutchhousing is rotationally supported within the transmission housing; afirst transmission input member rotatably supported in the transmissionhousing, a second transmission input member rotatably supported in thetransmission housing and wherein the second transmission input member isconcentric with the first transmission input member and at leastpartially surrounds the first transmission input member; a firstcountershaft rotatably supported within the transmission housing andspaced apart from and parallel with the first and second transmissioninput members; a second countershaft rotatably supported within thetransmission housing and spaced apart from and parallel with the firstand second transmission input members; a reverse gear selectivelyconnectable for common rotation to the first countershaft; a firstco-planar gear set having a first gear and a second gear, wherein thefirst gear is directly connected for common rotation with the secondtransmission input member and the second gear is selectively connectablefor common rotation to the second countershaft, wherein the second gearincludes a first gear teeth portion and a second gear teeth portion anda diameter of the first gear teeth portion is larger than a diameter ofthe second gear teeth portion, and wherein the first gear teeth portionmeshes with the first gear of the first gear set and the second gearteeth portion meshes with the reverse gear; a plurality of co-planargear sets interconnected between the first and second transmission inputshafts and the first and second countershafts; and four synchronizerassemblies for selectively coupling at least one of the co-planar gearsets with at least one of the first countershaft and the secondcountershaft, and wherein the selective engagement of the dual clutchassembly interconnects the dual clutch housing with at least one of thefirst and the second transmission input members and the selectiveengagement of at least one of the four synchronizer assembliesestablishes at least one of seven forward speed ratios.
 2. Thepowertrain of claim 1 wherein the plurality of co-planar gear setsincludes a second, third, fourth and fifth co-planar gear set, whereinthe second gear set includes a first gear in mesh with a second gear anda third gear, the third gear set includes a first gear in mesh with asecond gear and a third gear, the fourth gear set includes a first gearin mesh with a second gear, and the fifth gear set includes a first gearin mesh with a second gear.
 3. The powertrain of claim 2 wherein each ofthe first gears of the third, fourth and fifth gear set are directlyrotatably fixed for common rotation to the first transmission inputmember.
 4. The powertrain of claim 3 wherein each of the first gears ofthe first and second gear sets are directly rotatably fixed for commonrotation to the second transmission input member.
 5. The powertrain ofclaim 4 wherein the third gear of the second gear set, the third gear ofthe third gear set and the second gear of the fourth gear set are eachselectively connectable for common rotation with the first countershaftby two of the our synchronizer assemblies.
 6. The powertrain of claim 5wherein the second gear of the first gear set, the second gear of thesecond gear set, the second gear of the third gear set and the secondgear of the fifth gear set are each selectively connectable for commonrotation with the second countershaft by another two of the foursynchronizer assemblies.
 7. The powertrain of claim 6 wherein a first ofthe four synchronizer assemblies selectively connects at least one ofthe second gear of the first gear set and the second gear of the secondgear set to the second countershaft.
 8. The powertrain of claim 7wherein a second of the four synchronizer assemblies selectivelyconnects at least one of the reverse gear and third gear of the secondgear set to the first countershaft.
 9. The powertrain of claim 8 whereina third of the four synchronizer assemblies selectively connects atleast one of the second gear of the third gear set and the second gearof the fifth gear set to the second countershaft.
 10. The powertrain ofclaim 9 wherein a fourth of the four synchronizer assemblies selectivelyconnects at least one of the third gear of the third gear set and thesecond gear of the fourth gear set to the first countershaft.
 11. Thepowertrain of claim 6 wherein the first gear set is adjacent the dualclutch assembly, the second gear set is adjacent the first gear set, thethird gear set is adjacent the second gear set, the fourth gear set isadjacent the third gear set, and the fifth gear set is adjacent thefourth gear set.
 12. The powertrain of claim 1 further comprising afirst countershaft transfer gear fixed to the first countershaft forcommon rotation with the first countershaft and a second countershafttransfer gear fixed to the second countershaft for common rotation withthe second countershaft and wherein the first and second countershafttransfer gears transfer torque from at least one of the first and secondcountershafts to a transmission output member.
 13. The powertrain ofclaim 12 wherein the transmission output member is a gear that mesheswith the each of the first and second countershaft transfer gears. 14.The powertrain of claim 12 further comprising a park gear fixed to afirst end of a park gear shaft and a park transfer gear fixed to asecond end of the park gear shaft and wherein the park transfer gearmeshes with the transmission output member and wherein the park gear isconfigured to prevent rotation of the transmission output member whenthe park gear is engaged.
 15. The powertrain of claim 12 furthercomprising a park gear fixed to a first countershaft, wherein the parkgear is configured to prevent rotation of the first countershafttransfer gear and the transmission output member when the park gear isengaged.
 16. A transmission comprising: a transmission housing; a dualclutch assembly having a clutch housing connectable to an engine outputmember, wherein the clutch housing is rotationally supported within thetransmission housing and wherein the dual clutch assembly includes afirst clutch and a second clutch; a first, second, third, fourth andfifth gear set, wherein the first gear set includes a first gear in meshwith a second gear, the second gear set includes a first gear in meshwith a second gear and a third gear, the third gear set includes a firstgear in mesh with a second gear and a third gear, the fourth gear setincludes a first gear in mesh with a second gear, the fifth gear setincludes a first gear in mesh with a second gear, wherein the secondgear of the first gear set is a stepped pinion gear having a first and asecond gear teeth portions, and wherein the first gear teeth portionmeshes with the first gear of the first gear set and the second gearteeth portion meshes with a reverse gear; a first transmission inputmember rotatably supported in the transmission housing, and wherein eachof the first gears of the third, fourth and fifth gear set are rotatablyfixed for common rotation with the first transmission input member andwherein the first clutch of the dual clutch assembly is configured toselectively connect the dual clutch housing to the first transmissioninput member; a second transmission input member rotatably supported inthe transmission housing and, wherein each of the first gears of thefirst and second gear sets are rotatably fixed for common rotation withthe second transmission input member and wherein the second transmissioninput member is concentric with the first transmission input member andat least partially surrounds the first transmission input member andwherein the second clutch of the dual clutch assembly is configured toselectively connect the dual clutch housing to the second transmissioninput member; a first countershaft rotatably supported within thetransmission housing and spaced apart from and parallel with the firstand second transmission input members, wherein the reverse gear, thethird gear of the second gear set, the third gear of the third gear setand the second gear of the fourth gear set are each selectivelyconnectable for common rotation with the first countershaft; a secondcountershaft rotatably supported within the transmission housing andspaced apart from and parallel with the first and second transmissioninput members, wherein the second gear of the first gear set, the secondgear of the second gear set, the second gear of the third gear set andthe second gear of the fifth gear set are each selectively connectablefor common rotation with the second countershaft; four synchronizerassemblies for selectively coupling at least one of the co-planar gearsets with at least one of the first countershaft and the secondcountershaft, and wherein the selective engagement of the dual clutchassembly interconnects the dual clutch housing with at least one of thefirst and the second transmission input members and the selectiveengagement of at least one of the four synchronizer assembliesestablishes at least one of seven forward speed ratios.
 17. Atransmission comprising: a transmission housing; a dual clutch assemblyhaving a clutch housing connectable to an engine output member, whereinthe clutch housing is rotationally supported within the transmissionhousing and wherein the dual clutch assembly includes a first clutch anda second clutch; a first, second, third, fourth and fifth gear set,wherein the first gear set includes a first gear in mesh with a secondgear, the second gear set includes a first gear in mesh with a secondgear and a third gear, the third gear set includes a first gear in meshwith a second gear and a third gear, the fourth gear set includes afirst gear in mesh with a second gear, the fifth gear set includes afirst gear in mesh with a second gear, wherein the second gear of thefirst gear set is a stepped pinion gear that meshes with the first gearof the first gear set and with a reverse gear; a first transmissioninput member rotatably supported in the transmission housing, andwherein each of the first gears of the third, fourth and fifth gear setare rotatably fixed for common rotation with the first transmissioninput member and wherein the first clutch of the dual clutch assembly isconfigured to selectively connect the dual clutch housing to the firsttransmission input member; a second transmission input member rotatablysupported in the transmission housing and, wherein each of the firstgears of the first and second gear sets are rotatably fixed for commonrotation with the second transmission input member and wherein thesecond transmission input member is concentric with the firsttransmission input member and at least partially surrounds the firsttransmission input member and wherein the second clutch of the dualclutch assembly is configured to selectively connect the dual clutchhousing to the second transmission input member; a first countershaftrotatably supported within the transmission housing and spaced apartfrom and parallel with the first and second transmission input members,wherein the reverse gear, the third gear of the second gear set, thethird gear of the third gear set and the second gear of the fourth gearset are each selectively connectable for common rotation with the firstcountershaft; a second countershaft rotatably supported within thetransmission housing and spaced apart from and parallel with the firstand second transmission input members, wherein the second gear of thefirst gear set, the second gear of the second gear set, the second gearof the third gear set and the second gear of the fifth gear set are eachselectively connectable for common rotation with the secondcountershaft; a first synchronizer assembly selectively connects atleast one of the second gear of the first gear set and the second gearof the second gear set to the second countershaft; a second synchronizerassembly selectively connects at least one of the reverse gear and thirdgear of the second gear set to the first countershaft; a thirdsynchronizer assembly selectively connects at least one of the secondgear of the third gear set and the second gear of the fifth gear set tothe second countershaft; a fourth synchronizer assembly selectivelyconnects at least one of the third gear of the third gear set and thesecond gear of the fourth gear set to the first countershaft; and afirst countershaft transfer gear fixed to the first countershaft forcommon rotation with the first countershaft and a second countershafttransfer gear fixed to the second countershaft for common rotation withthe second countershaft and wherein the first and second countershafttransfer gears transfer torque from at least one of the first and secondcountershafts to a transmission output member, and wherein the selectiveengagement of dual clutch assembly interconnects the dual clutch housingwith at least one of the first and the second transmission input membersand the selective engagement of at least one of the synchronizerassemblies establishes at least one of seven forward speed ratios.